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ST. JOHN’S, N.L. – Hydroelectric projects will put more methylmercury pollution into northern ecosystems than climate change, suggests a new Harvard University study.

Methylmercury, a neurotoxin created as mercury blends with bacteria, is linked to heart issues and intellectual problems in children.

High levels of the substance in Arctic marine life have been traced to global warming as sea ice melts.

But the researchers say governments turning to hydroelectric dams as a cleaner way to curb climate change must consider potential effects of flooding vast swaths of land.

The peer-reviewed study, published in the latest issue of the U.S.-based “Proceedings of the National Academy of Sciences,” echoes concerns raised by Inuit leaders who fear methylmercury levels from the new Muskrat Falls dam in Labrador will soar.

The project will create a reservoir near Happy Valley-Goose Bay, upstream from Lake Melville and more than 2,000 Inuit who rely on fish and seal meat as prime food sources. First power is expected to flow in 2017.

Harvard researchers led by Elsie Sunderland, associate professor of environmental engineering and environmental health, measured baseline methylmercury levels in Lake Melville. They noted that concentrations in plankton peaked between one and 10 metres under the water, just as they do in the central Arctic Ocean.

The study concludes that when fresh and salt water meet — in estuaries such as Lake Melville or as oceans absorb melting sea ice — the salinity means organic matter that would usually sink begins to float. It forms a bacterial layer that marine plankton then feast on.

Postdoctoral fellow Amina Schartup, the study’s lead author, said the result is a very effective process for boosting toxic methylmercury.

“This system is very good at taking very low concentrations of methylmercury and making it relatively high in the plankton,” she said in an interview. Fish then eat the plankton.

Schartup wonders to what extent toxin levels then accelerate higher up the food chain.

“This is a whole other study that needs to happen,” she said. “I think we need to continue this work so if we do see spikes in the fish or in the water that could be potentially a problem, that we respond immediately before there is an impact on people’s health.”

Crown corporation Nalcor Energy is monitoring mercury levels but has said its projections suggest contamination in Lake Melville will be diluted to “no measurable effects.”

Nalcor did not answer a request for comment Tuesday.

The study was mainly funded by the independent National Science Foundation based in North Arlington, Va., with support from the Nunatsiavut government representing Inuit in the Lake Melville region. Its members contacted Sunderland to help with related research after Muskrat Falls environmental assessments predicted no adverse effects downstream.

Darryl Shiwak, Nunatsiavut’s minister of lands and natural resources, said Nalcor is not doing enough to set benchmarks against which potential contamination can be measured. He’s also calling for the clearing of all trees and vegetation from a reservoir site the province has estimated will cover about 120 square kilometres.

Shiwak, who lives in Rigolet, said he’s one of many people wondering how his ability to rely on fish and wild meat could be changed forever.

“Everybody’s calling for more hydroelectric projects because they’re better on the environment,” he said in an interview. “But what nobody is seeing is the cost of that project — the real, human cost.”